AMD recently launched its flagship RDNA 3 offering based on its Navi 31 GPUs, the Radeon RX 7900 series. While I pitted the AMD Navi 31 against NVIDIA’s RTX 4080, the final performance was a bit underwhelming and wasn’t the massive upset everyone expected. Rumors now suggest that the reason behind such lackluster performance could be due to the incomplete GPU silicon shipped on the main cards.
AMD Allegedly Shipped RDNA 3 ‘Navi 31’ GPU Silicon With Radeon RX 7900 Series Graphics Cards
As he discovered it Kepler 2It appears that early RDNA 3 silicone had a non-working pre-HW shader. This appeared in three chipsets, the GFX1100 (Navi 31), GFX1102 (Navi 33), and GFX1103 (an APU lineup consisting of Phoenix chipsets). It is now based on the latest GitHub submission. Kepler also suggests that Navi 32 GPUs are physically based on IP “GFX1103” while Navi 33 chipsets feature IP “GFX1102”. The same issues are found on every other chip besides Navi 32 which will be featured in many mainstream discrete GPUs on desktop and mobile platforms by early 2023.
So AMD decided to release Navi31 A0 silicon, which is known to have pre-shader for non-working fetch HW 🤦♂️🤦♂️🤦♂️🤦♂️https://t.co/cQTRKynN0B pic.twitter.com/CIdv6GUcYW
– Kepler (@Kepler_L2) December 14, 2022
According to Kepler, this is something that can’t be fixed or revised in a few weeks and will take several months if AMD plans to fix this. It would be a huge blow if the newer silicon showed up with the fix a few months later because the majority of gamers had already purchased the early revision of the Radeon RX 7900 series with the unfinished silicon. AMD will likely prepare an update a year later that will address these issues, but for now, the Radeon RX 7900 series may have to rely heavily on driver-level improvements to address the patchy GPU nature of their RDNA 3 silicon.
But that’s not all, other key features like VOPD instructions featured in RDNA 3 GPUs claimed to offer a significant performance improvement but in reality, they only managed to deliver a 4 percent improvement over RDNA 2 in ray tracing titles. The RDNA 3 silicon is designed to handle dual Wave32 instructions to double the floating point performance through the use of 64 multi-precision multi-purpose ALUs implemented across two SIMD32 modules. Speaking to an AMD representative, the folks over at HardwareTimes were able to confirm that AMD is currently working on performance tuning here and expect improvements along the way:
Wave64 can access new ALUs for 2x execution rates to unlock performance during heavy ALU code execution. For Wave32 mode, the compiler rearranges and packages the instructions into VOPD encoding. Our RT test scene using VOPD encodings provided an approximately 4% increase in frames per second by removing the ALU bottleneck. We expect to see more improvements as the compiler matures with more improvements for mapping code sequences to VOPD encodings. And with advances in using AI-based, root-based, and computing-based rendering technologies for more photorealistic rendering, we expect to see ALU-related symbols that will take advantage of these new ALUs more and more.
AMD rep via HardwareTimes
Reviewers who also got a first look at several AMD Radeon RX 7900 series dedicated graphics cards also reported inconsistent and choppy clock speeds on the cards.
Some really strange behavior with the ASUS TUF 7900 XT. It will run 2400MHz in one game, then 2900MHz in the next. All stock settings, with similar force pull. 🧐
– Nadalina (@NadaOverbeeke) December 14, 2022
It got weirder. First, MW2 (1080p) plays at 350fps with 2900MHz clocks. But after an hour and a reboot or 2 hours later, it’s running at 300fps with t~2400mhz.
Same game, same test run, same settings.
Now retesting the XTX, all of a sudden the same thing: +20% FPS out of nowhere. https://t.co/hvRCPzLqXV
– Nadalina (@NadaOverbeeke) December 14, 2022
Depending on the address, the 7900XTX can run anywhere from under 2.4GHz to just over 2.9GHz, all while sitting on or under 1V. This is a huge discrepancy.
I don’t think I’ve ever seen such a massive red flag when it comes to missing energy goals. pic.twitter.com/AEGWc424kk
– uzzi38 (@uzzi38) December 12, 2022
Here is a breakdown of all AMD GPU architectures released since Vega:
|Graphics engineering||GPU CODENAME||alternative name||Architectural Engineering||Producer|
|GFX900||Vega 10||GCN 5.0||RX VEGA / Radeon Pro|
|GFX902||black Crow||Raven Ridge / Picasso||GCN 5.0||Ryzen 2000/3000 (G/GE)|
|GFX904||Vega 12||GCN 5.0||Vega Pro 20 (Mac)|
|GFX906||Vega 20||GCN 5.0||Radeon VII / Radeon Pro VII|
|GFX908||Arcturus||CDNA 1||MI100 instinct|
|GFX90A||Aldebaran||CDNA 2||MI200 Instinct|
|GFX909||Crow 2||GCN 5.0||TBC|
|GFX909||Renoir||GCN 5.0||Ryzen 4000 (H/U/G)|
|GFX1010||Navi 10||RNA 1||RX 5700/5600 (M/XT)|
|GFX1011||Navi 12||RNA 1||PRO 5600M (MAC)|
|GFX1012||Navi 14||RNA 1||RX 5500 (M/XT)|
|(GFX 1030)||Navi 21||Big Navy / Sienna Cichlids||RNA 2||RX 6900/6800 series|
|(GFX1031)||Navi 22||marine flounder||RNA 2||RX 6700 series|
|GFX1032||Navi 23||Demagry Cavfish||RNA 2||RX 6600 series|
|(GFX 1033)||Navi 24||Goby beige||RNA 2||RX 6500/6400 series|
|(GFX 1033)||Van Gogh||Aerith||RNA 2||steam surface|
|(GFX 1036)||Raphael||RNA 2||Ryzen 7000?|
|GFX1040||Van Gogh Light / Mendocino||green sardines||RNA 2||Ryzen 7000?|
|GFX1100||Navi 31||Plum bonito||RNA 3||Radeon RX 7900|
|GFX1101||Navi 32||Wheat is people||RNA 3||Radeon RX 7800|
|GFX1102||Navi 33||Hotpink bonefish||RNA 3||Radeon RX 7700?|
|GFX1103||Navi 3X||Phoenix Point||RNA 3||Ryzen 7000 APU?|
|(GFX 1200)||Navi 4x||RNA 4||Radeon RX 8000?|
The days ahead for RDNA 3 and especially the Radeon RX 7900 graphics cards based on the Navi 31 GPU silicon will be interesting. Extreme overclockers have told us that they can’t install their cards at higher clock speeds since silicon is severely restricted by power limits and it makes absolutely no sense to do LN2 OC with existing BIOS.